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Troubleshooting

 

PRINTABLE VERSION

IMPORTANT NOTES: THIS DIAGRAM REPRESENTS ONLY ONE POSSIBLE STARTER WIRING SCENARIO.  THERE ARE OTHERS.  

DO NOT USE THIS DIAGRAM AS GUIDANCE FOR INSTALLING YOUR STARTER!   

Installation information is ALWAYS included with each starter and can also be found on the product specific  pages of this website (listed in blue blocks above left). 

 

Also,

DO NOT REMOVE THE STARTER FROM THE AIRCRAFT TO PERFORM TESTING! For accuracy and relevance, starter testing should be conducted in the aircraft while the starter is in its failure mode (start switch/button "on" but starter performance is not pleasing you). 

 

Do  NOT use jumper cables, a friend's battery, or auto store battery testers to test aircraft starter systems.  It never provides valuable/constructive troubleshooting  information. 

 

Use an analog voltmeter if at all possible. An ohmmeter will not provide useful information - keep it simple & follow these easy steps:

Pretest Considerations: If possible, visually inspect the starter and/or interview pilot/operators for starting history. Indications of long cranking periods, burning odor or smoke from the starter, kickback(s), a cracked starter mount, a fast spinning starter w/no prop movement (for Sky-Tec NL model starters replace shear pin), oil in starter, grinding noise or a damaged ring gear are generally indications that the starter is in need of repair and the following tests will not be helpful. Remove the starter for repair or overhaul (the NL model starter shear pin is FIELD REPLACEABLE - do not return to Sky-Tec for shear pin repair). 

Testing Relevance: The following testing procedure is most relevant to Lycoming starters and some Continental starters that are low performing including slow cranking and/or failure to crank the engine over a compression stroke. If a starter is damaged by overcranking or a stuck firewall solenoid, voltage in step one may read below acceptable levels thus incorrectly indicating a potential battery problem. Therefore, in such cases some consideration must be to the pretest conditions noted above (if it smells burned...). If the only effect of energizing the starter results only in an audible “click” with no prop movement, confirm step 2 to isolate problem to starter or starter contactor. 

For Sky-Tec CvST3 (Continental) model starters: Sky-Tec CvST3 starters feature an inspection port. If starter rotates but prop does not, remove inspection plug and note clutch drum rotatation. If rotation is observed, starter is OK - suspect starter adaptor. 

 

 

Start Here:

 

TEST RECORD

RESULT

ANALYSIS
Record voltage at the battery while cranking the starter in its failure mode.  

 

______

VOLTS

Below 11V / 22V? Yes - Voltage at battery drops below 11V / 22V?  
Questionable battery. See Testing Relevance above as a shorted (cooked) starter will pull voltage down appreciably. However, if starter rotates at all, this is generally not a shorted starter condition.  
Address battery issue - no need to proceed with remainder of troubleshooting.

 

No - Voltage at battery remains above 11V / 22V?  
Proceed to Step 2

Record voltage at the starter while cranking
the starter in its failure mode.

 

 

______

VOLTS

Below 10V / 20V? Yes - Voltage at starter drops below 10V / 20V?  
Not a starter problem.   The starter needs 10V / 20V to do its thing.  Below that, all bets are off.  Suspect Cables, terminals and/or solenoids.  Or maybe that airframe just isn't up to the task.  

If the difference between Step 1 and Step 2 is more than 2 volts, Proceed to Steps 3 & 4 to find airframe voltage losses.

 

No - Voltage at starter remains above 10V / 20V? And the starter's performance is not pleasing you?
Click here to return the starter to Sky-Tec for analysis/repair.  There is nothing more you can do.

OPTIONAL AIRFRAME VOLTAGE TROUBLESHOOTING  (Perform only if battery remains above 11V / 22V in Step 1 and starter receives less than 9V / 18V in Step 2) 
Record voltages between each and every cable 

terminal and across solenoids while cranking the 

starter in its failure mode.

Assuming the voltage difference noted in Step 2 exceeded 2V / 4V, flush out any appreciable loss in voltage in any cable or solenoid by placing the meter along each link in the diagram. A tight electrical system will lose no more than 0.5 volts between the battery and starter. Be sure to conduct these tests while cranking the starter in its failure mode (when it's powered but not pleasing you).
Record voltages between battery & ground 

and starter & ground while cranking the starter

in its failure mode.

If no appreciable loss of voltage is noted in Step 3, flush out the integrity of all electrical system grounds. Pay close attention to battery and engine grounds. Clean up or repair any questionable ground connections and re-test. 

 

Returning a Starter to Sky-Tec
After you've completed the troubleshooting process and determined the starter needs servicing, click here to obtain a Return Authorization number online. 

 

Common Complaints and Credible Culprits
 

  Complaint Question Culprit
The Bump & Run When starter engages, the prop moves (some distance), and then stalls on the first compression stroke.  After repeated attempts, starting is successful (usually). Does it happen any more (or less) when the engine is hot? Voltage.  Rarely a starter issue.  Sky-Tec starters do not have a "weak" state.  Provided sufficient voltage, they either work great or don't work at all.  Typically, this slowing of the cranking is a sign of a loss of voltage.  If it happens when hot, suspect bad cables or solenoids.  If it happens when cold (or always), suspect a bad battery.  But the Troubleshooting Test (above) can help isolate the voltage loss. 
The Bump & Grind When starter engages, it makes a terrible  "grinding" noise. Has the engine ever had a kickback when cranking? A spark before Top-Dead-Center while cranking will break starters (and other accessories as well).  In the case of old, heavyweight starters, kickbacks broke teeth off the ring gear. Sky-Tec LS/PM & HT starters (excl. HTI starters) are designed to break when an engine fires before top-dead-center during cranking.  In some cases, they bend instead of breaking giving the illusion that they're up to the task but the grinding noise is an indicator not everything is well.  Fix the ignition problem then send that starter in for a repair.
Clicks & Crickets When we attempt to engage the starter, we hear a "click" but  NOTHING happens  Run the Toubleshooting Test (above) 
What is the voltage while cranking at the starter?
If the starter is not getting voltage, suspect the aircraft's firewall solenoid or switch.  

If the starter is receives >10V / 20V, suspect the starter's on board solenoid has failed (if so equipped).   Send that starter in for a new solenoid.
Clicks & Crickets with the smell of burned metal  When we attempt to engage the starter, we hear a "click" but  NOTHING happens.   Smell your starter (hey, dogs do far worse).  Does it smell burned?

 

Does the battery pull down excessively when you energize the starter?

Well, a fried starter is caused by one of three things:

1) The switch failed and held closed even when released (kept the starter solenoid/starter engaged for a period of time that exceeded the published operating limitations).

2) The firewall solenoid stuck/welded for a period of time that exceeded the published operating limitations,

or


3) The yoke actuator (pilot/operator) held the starter switch on in excess of the published operating limitations,

 

You best send that starter in for a repair.

Don't Let Go After start button is released, the starter stays engaged for nearly a second before releasing. Does it stay engaged only for 1/2 to 2 seconds? This is normal operation for a permanent magnet starter (Sky-Tec LS, PM, & ST2, ST3 and ST5, models).  Although power is removed by releasing the key/start button, a permanent magnet motor will actually provide power to itself as it winds-down and will keep the starter drive engaged for about a half-second until it loses sufficient RPM to fully disengage.  Normal!
Hang 'em High It appeared as though the starter drive gear stayed engaged for some length of time after the start button/key was released Did you see smoke?  Does the starter smelled like burnt metal? A stuck firewall solenoid (starter contactor) can ruin your day AND your starter.  Many older Cessna and Piper aircraft starter contactors are notorious for "welding shut" after years of use (often accelerated by the use of a high-current draw starter).  Some of those older contactors (or relays as the case is) just cannot handle the increased starting current loads over a length of time.  In some cases, the manufacturer even specified the wrong kind of starter solenoid in the application in the first place (see Cessna Firewall Solenoids).  You may have few options besides overhauling or replacing your starter after replacing the culprit firewall solenoid.

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